Free piston engine with air compression on power stroke



FREE PISTON ENGINE WITH AIR COMPRESSION ON POWER STRQKE J. R. RUGGERI Filed Jan. 24, 1958 Cfofin R. Ru erz' PM 0. W

United States Paton-t FREE PISTON ENGINE WITH AIR COMPRESSION ON POWER STROKE Application January 24, 1958, Serial No. 711,058

1 Claims. 01. 123-46) This invention relates to a free piston engine. More particularly it relates to a free piston engine having an improved arrangement for the compression of air.

The conventional free piston engine comprises a casing having an elongated cylinder, a central portion of which constitutes a combustion chamber. The casing also includes at opposite ends a pair of bounce chambers and a compressed air chamber which surrounds the cylinder. A pair of power pistons are positioned within the cylinder for inward and outward movement, each power piston having connected thereto a bounce piston which during the bounce or inward stroke is adapted to force air inwardly into the compressed air chamber. The compressed air chamber by means of scavenging openings discharges air through these openings into the cylinder during the outermost stroke of the power pistons whereby the gases and compressed air escape through exhaust openings thereby creating a force for driving a gas turbine etc. Thus in the conventional free piston engine the bounce pressure operates to return the power pistons to their original position and simultaneously force air under compression into the compressed air chamber. The energy which serves to return the power pistons to their initial position is effected by the compression of air on one side of the bounce piston during the power stroke of the power piston. Since the inward compression type of free piston engine pumps air into the compressed air chamber while simultaneously returning the bounce piston and power piston to their original positions, the forces are such that pressure fluctuations occur in the compressed air chamber. These fluctuations are not desirable. In view of the fluctuations in pressure occurring in the conventional engine, it is also necessary to have a fairly large sized compressed air chamber. This of necessity requires a larger engine dimension which in most instances is highly undesirable.

It is a prime object of this invention, therefore, to

provide an improved free piston engine wherein the pressure fluctuations within the compressed air chamber are greatly reduced. It is a still further object to provide an improved free piston engine wherein the compression of air to the compressed air chamber occurs during the power stroke of the engine.

A still further object of the invention is to provide an improved free piston engine wherein the compressor pistons and the power pistons are interconnected in such amanner that the compression of air occurs during the power stroke of the engine.

A still further object is to provide an improved free piston engine wherein the compression of air into the compressed air chamber follows a consistent pattern in view of the positive action ofthe: compressor pistons operating directly during the power stroke of the power pistons. v t These and other objects will become more readily ap parent from a reading of the description when examined ice in connection with the accompanying sheet of drawing.

In the drawing:

Figure 1 is a cross-sectional view lengthwise through an improved free piston engine with certain portions broken away to illustrate certain features; and

Figure 2 is a cross-sectional view taken substantially along the line 2-2 of Figure 1.

Referring now to Figure 1, a free piston engine is generally designated by the reference character 10. The free piston engine comprises a casing 11 having a centrally disposed elongated cylinder 12. The cylinder 12 is provided with a central combustion chamber 13, the said cylinder 12 being suitably supported on longitudinally spaced walls 14 formed on the casing 11. A compressed air chamber 15 encircles the cylinder 12, the said compressed air chamber 15 being disposed between the walls 14. The upper end of the casing 11 is provided with a recess 16 and a cylindrical member 17 has supported therein an injection nozzle 18 for directing fuel into the combustion chamber 13.

Opposite ends of the casing 11 are provided with a pair of cylindrical walls 19 of lesser diameter than the diameter of the casing 11, the said cylindrical walls 19 being positioned outwardly of the walls 14 and providing a pair of bounce chambers 20. Surrounding the said cylindrical Walls 19 are accumulating chambers 21. Each wall 14 may be provided with a plurality of valves 22, only one valve 22 being shown on each wall 14 for the purpose of illustration. Each valve 22 opens inwardly into the compressed air chamber 15 during a certain air pressure within-the accumulating chambers 21. The casing is also provided with a plurality of valves 22'. These valves opening inwardly into the accumulating chambers 21 during a predetermined minus pressure within the accumulating chambers 21.

A pair of opposed power pistons 23 are slidingly positioned within the'cylinder 12. The power pistons 23 2 include suitable rings 24 and a sealing ring 25 is positioned on opposite ends of the cylinder 12 for engaging each of the power pistons 23. Each power piston 23 has connected thereto a bounce piston 26, the said bounce pistons 26 being slidingly disposed in the cylinders 19. The

bounce pistons 26 also include suitable piston rings 27.

Each accumulating chamber 21 has slidingly positioned therein a compressor piston 28 having outer surfaces 29 and inner surfaces 30. The inner surfaces 30 support piston rings 31 and the outer surfaces 29 support piston rings 32.

The cylinder 12 is provided with a plurality of circumferentially extending scavenging openings 33 communicating with the compressed air chamber 15 and being adapted to direct air under compression to the combustion chamber 13 on the outer stroke of the pistons 23.

The cylinder 12 is further provided with a plurality of circu-mferentially extending exhaust openings 34 which communicate with an exhaust duct 35 to permit the exhaust of gases from the combustion chamber 13 during the outer power stroke of the pistons 23.

A pair of connecting rods are designated by the reference character 36. Each connecting rod 36 slidingly extends through openings 37 and 38 provided in the spaced walls 14. Each connecting rod 36, also as indicated at 39, is connected to one of the compressor pistons 28 and at its opposite end is connected to one of the bounce pistons 26 which is disposed at the opposite end of the casing 11. Thus the compressor piston 28 at one end of the casing is connected to the bounce piston 26 disposed at the opposite end of the casing. 1

A rack 40 is also connected to each bounce piston'26, the said' racks being of conventional construction and being in engagement with a pinion 41 suitably rotatably supported on a shaft 42 connected to the cylinder 12.

; The rack andpinion constructionis conventional and is camera for the purpose of keeping the power pistons 23 properly synchronized during the operation.

In the operation, fuel is injected into the combustion chamber 13 and by suitable ignition means (not shown) the fuel is ignited whereupon the power pistons 23 move in an outward direction. The bounce pistons 26 move outwardly compressing the air contained within the bounce chambers 29. During the outward movement of the power pistons 23, and bounce pistons 26, the compressor pistons 28 are moved in an inward direction whereupon air within the accumulating chambers 21 is forced through the valve 22 into the compressed air chamber. During this inward stroke the valves 22 are closed. Thus air is compressed within the compressed air. chamber 15 and as the power pistons 23 reach the outermost position the openings 33 and 34 are in communication with the combustion chamber 13. The compressed air from the compressed air chamber now enters the combustion chamber through the scavenging openings 33 and the exhaust is discharged through the openings 34 to the duct 35 and from there to a gas turbine, etc.

The compressed air in the bounce chambers 20 now forces the pistons 26 and 23 again in-an inward direction whereupon the compressor pistons 28 move outwardly and the valves 22' open to permit air to enter from the atmosphere into the accumulating chambers 21.

Thus the complete cycle of operation has been described and it is of particular significance to note that the compression of air into the compressed air chamber occurs on the outward stroke of the power pistons 23 and on the inward stroke of the compressor piston 28. Thus entry of air into the compressed air chamber 15 occurs while the power pistons 23 are being forced outwardly under the influence of the expanding gases within the chamber 13. Thus positive equal forces serve to pro vide for the compression of air into the compressed air chamber. By the positive reactions of the power pistons during the power stroke, the compression of air within the compressed air chamber is constant and less pressure drops occur within said chamber than with the conventional design wherein the bounce piston compresses the air during the inward stroke resulting from the pressures in the bounce chamber. Since the pressure drop is less in the improved design, the compressed air chamber 15 may have a lesser volume capacity thus permitting a smaller engine to be designed. Also with the arrangement shown, the peak pressures obtained in the compressed air chamber are lower and the higher pressures are not required in view of the positive action of the compressor pistons 28 during the power stroke of the power pistons 23.

Thus it is apparent that an improved free piston engine design has been described which will fully meet the stated objects of this invention. It must be understood, however, that modifications and changes may be made which do not depart from the spirit of the invention as disclosed or the scope thereof as defined in the appended claims.

What is claimed is:

1. A free piston engine comprising a casing having an elongated cylinder comprising a combustion chamber, opposed power pistons slidingly positioned in said cylinder, a pair of bounce chambers positioned at opposite ends of said casing, a bounce piston connected to each power piston, each bounce piston being positioned for reciprocation in one of said bounce chambers, a com.- pressed air chamber surrounding said cylinder, 21 pair of accumulating chambers disposed at opposite ends of said casing and surrounding said bounce chambers, a pair of longitudinally spaced walls separating said accumulating chambers from said compressed air chamber, a valve in each wall opening inwardly with respect to said compressed air chamber, said casing including valves opening inwardly into said accumulating chambers, means for directing :fuel to said combustion chamber, a compressor piston reciprocally positioned in each accumulating chamber, and means connecting each bounce piston dis posed at one end of the casing to a compressor piston disposed at the opposite end of said casing, comprising a pair of connecting rods, said connecting rods each being connected to one bounce piston, extending through said compressed air chamber into said accumulating chambers and being connected to said compressor pistons, whereby during the outward power strokes of said power pistons said compressor pistons are moved inwardly to discharge air from said accumulating chambers through the valves of said walls to said compressed air chamber.

2. A free piston engine comprising a casing having an elongated cylinder comprising a combustion chamber, opposed power pistons slidingly positioned in said cylinder, a pair of bounce chambers positioned at opposite ends of said casing, a bounce piston connected to each power piston, each bounce piston being positioned for reciprocation in one of said bounce chambers, a compressed air chamber adjacent said cylinder, a pair of accumulating chambers disposed at opposite ends of said casing adjacent said bounce chambers, a pair of longitudinally spaced walls separating said accumulating chain.- bers from said compressed air chamber, a valve in each wall to provide communication between the accumulating chambers and the compressed air chamber, said casing including valves adapted to provide communication with the atmosphere and said accumulating chambers, means for directing fuel to said combustion chamber, a compressor piston reciprocally positioned in each accumulating chamber, and means connecting each bounce piston disposed at one end of the casing to a compressor piston disposed at the opposite end of said casing, com prising a pair of connecting rods, said connecting rods each being connected to one bounce piston, extending through said compressed air chamber into said accumulating chambers and being connected to said compressor pistons, whereby during the outward power strokes of said power pistons said compressor pistons are moved inwardly to discharge air from said accumulating chambers through the valves of said walls to said compressed air chamber.

3. A free piston engine comprising a casing having an elongated cylinder comprising a combustion chamber, opposed power pistons slidingly positioned in said cylinder, a pair of bounce chambers positioned at opposite ends of said casing, a bounce piston connected to each power piston, each bounce piston being positioned for reciprocation in one of said bounce chambers, a compressed air chamber adjacent said cylinder, a pair of accumulating chambers disposed at opposite ends of said casing adjacent said bounce chambers, a pair of longitudinally spaced walls separating said accumulating chambers from said compressed air chamber, a valve in each wall to provide communication between the accumulating chambers and the compressed air chamber, said casing including valves adapted to provide communication with the atmosphere and said accumulating chambers, means for directing fuel to said combustion chamber, a compressor piston reciprocally positioned in each accumulating chamber, and means connecting each bounce piston disposed at one end of the casing to a compressor piston disposed at the opposite end of said casing, comprising a pair of connecting rods, said connecting rods each being connected to one bounce piston, and being connected to said compressor pistons, whereby during the outward power strokes of said power pistons said compressor pistons are moved inwardly to discharge air from said accumulating chambers through the valves of said walls to said compressed air chamber. i

4. A free pistonengine comprising a casing having an elongated cylinder comprising a combustion chamber, opposed power pistons slidingly positioned in said cylinder, a pair of bounce chambers positioned at opposite ends of said casing, a bounce piston connected to each power piston, each bounce piston being positioned for reciprocation in one of said bounce chambers, a compressed air chamber adjacent said cylinder, a pair of accumulating chambers disposed at opposite ends of said casing adjacent said bounce chambers, a pair of longitudinally spaced walls separating said accumulating chambers from said compressed air chamber, a valve in each wall to provide communication between the accumulating chambers and the compressed air chamber, said casing including valves adapted to provide communication with the atmosphere and said accumulating chambers, means for directing fuel to said combustion chamber, a compressor piston reciprocally positioned in each accumulating chamber, and means connecting each bounce piston disposed at one end of the casing to a compressor piston disposed at the opposite end of said casing, whereby during the outward power strokes of said power pistons said compressor pistons are moved inwardly to discharge air from said accumulating chambers through the valves of said walls to said compressed air chamber.

5. A free piston engine comprising a casing having an elongated cylinder comprising a combustion chamber, a pair of piston assemblies including opposed power pistons slidingly positioned in said cylinder, a pair of bounce chambers positioned at opposite ends of said casing, said piston assembly including a bounce piston connected to each power piston, each bounce piston being positioned for reciprocation in one of said bounce chambers, a compressed air chamber adjacent said cylinder, a pair of accumulating chambers disposed at opposite ends of said casing adjacent said bounce chambers, 21 pair of longitudinally spaced walls separating said accumulating chambers from said compressed air chamber, a valve in each wall to provide communication between the accumulating chambers and the compressed air chamber, said casing including valves adapted to provide communication with the atmosphere and said accumulating chambers, means for directing fuel to said combustion chamber, a compressor piston reciprocally positioned in each accumulating chamber, and means connecting each piston assembly disposed at one end of the casing to a compressor piston disposed at the opposite end of said casing, comprising a pair of connecting rods, said connecting rods each being connected to one piston assembly, extending through said compressed air chamber into said accumulating chambers and being connected to said compressor pistons, whereby during the outward power strokes of said power pistons said compressor pistons are moved inwardiv to discharge air from said accumulating chambers through the valves of said walls to said compressed air chamber.

6. A free piston engine comprising a casing, a cylinder on said casing, said cylinder having a combustion cham her, a pair of power pistons in said cylinder movable outwardly from one position in response to power gen erated in said combustion chamber, means associated with said power cylinders for returning said power pistons to their first position, a compressed air chamber on said casing, a pair of accumulating chambers disposed at opposite ends of said casing, a compressor piston reciprocal within each of said accumulating chambers, said casing including valve means responsive to movement in one direction of said compressor piston to provide communication between said accumulating chambers and said compressed air chamber, and a pair of connector means, each connector means having an end connected to one power piston adjacent one end of said casing and an opposite end connected to a compressor piston positioned adjacent the other end of said casing whereby during the outward movement of each power piston, the compressor pistons are moved inwardly to direct air from said accumulating chambers through said valves to said compressed air chamber.

7. A free piston engine comprising a casing, a cylinder on said casing, said cylinder having a combustion chambet, a pair of power pistons in said cylinder movable outwardly from one position in response to power generated in said combustion chamber, means associated with said power cylinders for returning said power pistons to their first position, a compressed air chamber on said casing, a pair of accumulating chambers disposed at opposite ends of said casing, a compressor piston reciprocal within each of said accumulating chambers, said casing including valve means responsive to movement in one direction of said compressor piston to provide communication between said accumulating chambers and said compressed air chamber, and means interconnecting each power piston with each compressor piston whereby during the outward movement of said power pistons said compressor pistons are moved inwardly to direct air through said valves to said compressed air chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,671,435 Spier et a1. Mar. 9, 1954 

